Influence of cross‐sectional velocity profile on flow characteristics of arterial wall modeled as elastic and viscoelastic material

2021 ◽  
Author(s):  
Mohammad Hasan ◽  
Badri Prasad Patel ◽  
Sathyasimha Pradyumna
Keyword(s):  
Velocity Profile ◽  
Viscoelastic Material ◽  
Arterial Wall ◽  
Flow Characteristics ◽  
Cross Sectional

scholarly journals Linking cardiorespiratory fitness classification criteria to early subclinical atherosclerosis in children

2015 ◽  
Vol 40 (4) ◽  
pp. 386-392 ◽  
Author(s):  
Xavier Melo ◽  
Helena Santa-Clara ◽  
Diana A. Santos ◽  
Nuno M. Pimenta ◽  
Cláudia S. Minderico ◽  
...  
Keyword(s):  
Cardiorespiratory Fitness ◽  
Arterial Wall ◽  
Operating Characteristic ◽  
Screening Tool ◽  
Subclinical Atherosclerosis ◽  
Intima Media Thickness ◽  
Carotid Intima Media Thickness ◽  
Cross Sectional Study ◽  
Cross Sectional ◽  
High Resolution Ultrasonography

It is unclear if cardiorespiratory fitness (CRF) can be used as a screening tool for premature changes in carotid intima-media thickness (cIMT) in paediatric populations. The purpose of this cross-sectional study was 3-fold: (i) to determine if CRF can be used to screen increased cIMT; (ii) to determine an optimal CRF cut-off to predict increased cIMT; and (iii) to evaluate its ability to predict increased cIMT among children in comparison with existent CRF cut-offs. cIMT was assessed with high-resolution ultrasonography and CRF was determined using a maximal cycle test. Receiver operating characteristic analyses were conducted in boys (n = 211) and girls (n = 202) aged 11–12 years to define the optimal sex-specific CRF cut-off to classify increased cIMT (≥75th percentile). Logistic regression was used to examine the association between the CRF cut-offs with the risk of having an increased cIMT. The optimal CRF cut-offs to predict increased cIMT were 45.81 and 34.46 mL·kg−1·min−1 for boys and girls, respectively. The odds-ratios for having increased cIMT among children who were unfit was up to 2.8 times the odds among those who were fit (95% confidence interval: 1.40–5.53). Considering current CRF cut-offs, only those suggested by Adegboye et al. 2011. (Br. J. Sports Med. 45(9): 722–728) and Boddy et al. 2012 (PLoS One, 7(9): e45755) were significant in predicting increased cIMT. In conclusion, CRF cut-offs (boys: ≤ 45.8; girls: ≤ 34.5 mL·kg−1·min−1) are associated with thickening of the arterial wall in 11- to 12-year-old children. Low CRF is an important cardiovascular risk factor in children and our data highlight the importance of obtaining an adequate CRF.

Effects of Nano-Nozzles Cross-Sectional Geometry on Fluid Flow: Molecular Dynamic Simulation

2017 ◽  
Vol 34 (5) ◽  
pp. 667-678 ◽  
Author(s):  
H. Nowruzi ◽  
H. Ghassemi
Keyword(s):  
Fluid Flow ◽  
Velocity Profile ◽  
Cross Sections ◽  
Md Simulation ◽  
Flow Behavior ◽  
Water Model ◽  
Physical Parameters ◽  
Cross Sectional ◽  
Behavior Characteristics ◽  
Fanning Friction Factor

AbstractNano-nozzles are an essential part of the nano electromechanical systems (NEMS). Cross-sectional geometry of nano-nozzles has a significant role on the fluid flow inside them. So, main purpose of the present study is related to the effects of different symmetrical cross-sections on the fluid flow behavior inside of nano-nozzles. To this accomplishment, five different cross-sectional geometries (equilateral triangle, square, regular hexagon, elliptical and circular) are investigated by using molecular dynamics (MD) simulation. In addition, TIP4P is used for atomistic water model. In order to evaluate the fluid flow behavior, non-dimensional physical parameters such as Fanning friction factor, velocity profile and density number are analyzed. Obtained results are shown that the flow behavior characteristics appreciably depend on the geometry of nano-nozzle's cross-section. Velocity profile and density number for five different cross sections of nano-nozzle at three various measurement gauges are presented and discussed.

scholarly journals Bayesian Optimization Design of Inlet Volute for Supercritical Carbon Dioxide Radial-Flow Turbine

Machines ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 218
Author(s):  
Chao Bian ◽  
Shaojie Zhang ◽  
Jinguang Yang ◽  
Haitao Liu ◽  
Feng Zhao ◽  
...  
Keyword(s):  
Optimization Design ◽  
Radial Flow ◽  
Flow Characteristics ◽  
Bayesian Optimization ◽  
Working Fluid ◽  
Cross Sectional ◽  
Pressure Loss Coefficient ◽  
Flow Capacity ◽  
Cycle Efficiency ◽  
Total Pressure Loss Coefficient

The radial-flow turbine, a key component of the supercritical CO2 (S-CO2) Brayton cycle, has a significant impact on the cycle efficiency. The inlet volute is an important flow component that introduces working fluid into the centripetal turbine. In-depth research on it will help improve the performance of the turbine and the entire cycle. This article aims to improve the volute flow capacity by optimizing the cross-sectional geometry of the volute, thereby improving the volute performance, both at design and non-design points. The Gaussian process surrogate model based parameter sensitivity analysis is first conducted, and then the optimization process is implemented by Bayesian optimization (BO) wherein the acquisition function is used to query optimal design. The results show that the optimized volute has better and more uniform flow characteristics at design and non-design points. It has a smoother off-design conditions performance curve. The total pressure loss coefficient at the design point of the optimized volute is reduced by 33.26%, and the flow deformation is reduced by 54.55%.

Cross-Sectional Elastic Imaging of Arterial Wall Using Intravascular Ultrasonography

2001 ◽  
Vol 40 (Part 1, No. 7) ◽  
pp. 4753-4762 ◽  
Author(s):  
Hitoshi Mita ◽  
Hiroshi Kanai ◽  
Yoshiro Koiwa ◽  
Masataka Ichiki ◽  
Fumiaki Tezuka
Keyword(s):  
Arterial Wall ◽  
Intravascular Ultrasonography ◽  
Cross Sectional

scholarly journals Performance and Exit Flow Characteristics of Mixed-Flow Turbines

1997 ◽  
Vol 3 (4) ◽  
pp. 277-293 ◽  
Author(s):  
C. Arcoumanis ◽  
R. F. Martinez-Botas ◽  
J. M. Nouri ◽  
C. C. Su
Keyword(s):  
Steady State ◽  
Velocity Ratio ◽  
Tangential Velocity ◽  
Flow Characteristics ◽  
Mixed Flow ◽  
Cross Sectional ◽  
Flow Angle ◽  
Turbine Efficiency ◽  
And Performance ◽  
Inlet Angle

The performance and exit flow characteristics of two mixed-flow turbines have been investigated under steady-state conditions. The two rotors differ mainly in their inlet angle geometry, one has a nominal constant incidence (rotor B) and the other has a constant blade angle (rotor C), but also in the number of blades. The results showed that the overall peak efficiency of rotor C is higher than that of rotor B. Two different volutes were also used for the tests, differing in their cross-sectional area, which confirm that the new larger area volute turbine has a higher efficiency than the old one, particularly at lower speeds, and a fairly uniform variation with velocity ratio.The flow exiting the blades has been quantified by laser Doppler velocimetry. A difference in the exit flow velocity for rotors B and C with the new volute was observed which is expected given their variation in geometry and performance. The tangential velocities near the shroud resemble a forced vortex flow structure, while a uniform tangential velocity component was measured near the hub. The exit flow angles for both rotor cases decreased rapidly from the shroud to a minimum value in the annular core region before increasing gradually towards the hub. In addition, the exit flow angles with both rotors were reduced with increasing rotational speeds. The magnitude of the absolute flow angle was reduced in the case of rotor C, which may explain the improved steady state performance with this rotor. The results also revealed a correlation between the exit flow angle and the performance of the turbines; a reduction in flow angle resulted in an increase in the overall turbine efficiency.

Flow Characteristics of Pulsating Flow Obstructed by an Array of Square Rods

2000 ◽  
Author(s):  
Hiroyuki Murata ◽  
Ken-ichi Sawada ◽  
Michiyuki Kobayashi
Keyword(s):  
Pressure Gradient ◽  
Flow Characteristics ◽  
Pulsating Flow ◽  
Pulsation Period ◽  
Simulation Code ◽  
Cross Sectional ◽  
Gradient Parameter ◽  
Streamwise Pressure Gradient ◽  
Time Variations ◽  
Visualization Experiments

Abstract A series of flow visualization experiments of pulsating flow obstructed by an array of square rods was carried out to investigate its characteristics. When the pulsation is absent, Karman vortices shed periodically from each rod. When the pulsation period is relatively long compared with the shedding period and its amplitude is large, the flow is stabilized during the accelerating phase and, during the decelarating phase, the flow is destabilized and Karman vortices break down. When the pulsation period is shorter than shedding period and its amplitude is large, the flow pulsation controls the generation and breakdown of the Karman vortices. A numerical simulation code was developed and compared with the experimental results. When the pressure gradient parameter of the code is changed sinusoidally with time, computed results become the pulsating flow. Time variations of the streamwise pressure gradient and cross-sectional averaged velocity show similarity between the experimental and computed results.

Cardiovascular Disease as a Late Complication of End-Stage Renal Disease in Children

2005 ◽  
Vol 25 (3_suppl) ◽  
pp. 123-126 ◽  
Author(s):  
Jaap Groothoff ◽  
Mariken Gruppen ◽  
Eric De Groot ◽  
Martin Offringa
Keyword(s):  
Cardiovascular Disease ◽  
Aortic Valve ◽  
Renal Disease ◽  
End Stage Renal Disease ◽  
Arterial Wall ◽  
Aortic Valve Calcification ◽  
Cross Sectional ◽  
Valve Calcification ◽  
Stage Renal Disease ◽  
End Stage

♦ Objective To analyze the late cardiovascular outcome of end-stage renal disease (ESRD) in children. ♦ Design A nation-wide long-term follow-up study. Determinants of outcomes and causes of death were retrospectively assessed. Patients underwent assessment of overall health state, B- and M-mode ultrasound of the carotid arteries, and echocardiography for cross-sectional analysis. ♦ Results We analyzed the medical course of all 249 adult Dutch patients with ESRD onset between 1972 and 1992 at age 0 – 14 years, and who were born before 1979. Of the 187 living patients, 140 participated in the cross-sectional part of the study. The standardized mortality rate was 31.0. Overall 5-, 10-, and 20-year survival after ESRD onset was 87%, 82%, and 78%, respectively. Cardiovascular disease accounted for most deaths (41%). In the whole group, left ventricular hypertrophy (LVH), aortic valve calcification, and arterial wall stiffening were highly prevalent. LVH was associated with hypertension at time of assessment. Aortic valve calcification was strongly associated with a long total duration of peritoneal dialysis (β = 0.33, p < 0.001). Arterial wall pathology was not associated with current treatment modality. ♦ Conclusions As in adults, cardiovascular disease is the most important cause of death in children with ESRD. Stricter reduction of volume overload, prevention of high serum calcium–phosphate product, and more vigorous treatment of hypertension are important targets to improve cardiovascular survival in children with ESRD.

Fluid flow analysis of cilia beating in a curved channel in the presence of magnetic field and heat transfer

2020 ◽  
Vol 98 (2) ◽  
pp. 191-197 ◽  
Author(s):  
Hina Sadaf ◽  
S. Nadeem
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Velocity Profile ◽  
Flow Analysis ◽  
Fluid Motion ◽  
Flow Characteristics ◽  
Physical Parameters ◽  
Curved Channel ◽  
Radial Magnetic Field ◽  
Fluid Flow Analysis

This paper investigates fluid motion generated by cilia and a pressure gradient in a curved channel. The flow analysis is carried out in the presence of heat transfer and radial magnetic field. The leading equations are simplified under the familiar suppositions of large wavelength and small Reynolds number approximations. An exact solution has been developed for the velocity profile. The flow characteristics of the viscous fluid are computed in the presence of cilia and metachronal wave velocity. The effects of several stimulating parameters on the flow and heat transfer are studied in detail through graphs. It is found that symmetry of the velocity profile is broken owing to bending of the channel. The radially varying magnetic field decreases the velocity field, but near the left ciliated wall it induces the opposite behavior. It is also found that velocity profile increases due to increase in buoyancy forces throughout the domain. Numerical consequences for velocity profile are also accessible in the table for diverse values of the physical parameters.

Compressible Shear Flows in the Duct with Varying Cross-Sectional Area

1967 ◽  
Vol 71 (674) ◽  
pp. 128-132
Author(s):  
S. Fujii
Keyword(s):  
Differential Equation ◽  
Velocity Profile ◽  
Radial Velocity ◽  
Combined Effects ◽  
Sectional Area ◽  
Cross Sectional ◽  
Rotational Flows ◽  
Axial Velocity Profile ◽  
Actuator Disc ◽  
Radial Velocity Profile

Summary:The basic theory of the compressible non-swirling rotational flows through ducts with varying hub radii, associated with the concept of actuator discs, is described. The problem is simplified by considering a single-parameter in the radial velocity profile. Particular attention is given to the combined effects of the taper of inside walls and also of compressibility on the radial velocity and the axial velocity profile. The derived ordinary differential equation with non-homogeneous terms can be reduced to the well-known formula of classical actuator disc theories for the cylindrical passage. A numerical example is also presented.

Matching Optimization of Impeller and Volute for Double-Channel with Double-Suction Pump

2014 ◽  
Vol 904 ◽  
pp. 311-314
Author(s):  
Bao Jie Luo ◽  
Lin Long Song ◽  
Pan Zhao
Keyword(s):  
Flow Characteristics ◽  
Prediction Method ◽  
Cross Sectional ◽  
Suction Pump ◽  
Uniform Distributions ◽  
Calculation Results ◽  
Tongue Position ◽  
Frequency Components ◽  
Suspended Matters ◽  
Double Channel

In order to study the matching optimization of the impeller and volute as well as the flow characteristics of double-channel with double-suction pump ,this paper based on CFD performance prediction method uses the same impeller to match the volute with different base diameters, guaranteeing the volute inlet width, flow cross-sectional area, and tongue position unchanged .The calculation results show that scheme A with the largest volute base diameter can not only achieve the excellent energy characteristics and the velocity-pressure uniform distributions, but also the exchange of the fluid energy is more sufficient in the volute. On one hand, a large clearance can not only make the movement interference intensity weaken between the impeller and volute, but also can decrease the high frequency components of the pressure pulsations .On the other hand, the big gap can maximum exert the pump effects to convey liquids containing solid suspended particles as well as the fibrous suspended matters. The research can not only provide some references to further study on matching optimization of the impeller and volute but also can contribute to the hydraulic design of the impeller and volute.

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